This invention relates to new and useful improvements in a pneumatic distributing device and particularly though not exclusively to such devices which are adapted to distribute granular or particulate material such as fertilizer, herbicide or seeds which can be broadcast over the ground or which can be applied to the soil using a cultivator or similar ground working device.
Various forms of broadcasting devices for fertilizer or herbicide are known. These can comprise structures for mounting on a vehicle or can comprise for example a pull-type vehicle with booms which extend to either side of the vehicle which can be extremely wide and may extend up to sixty or eighty feet in width.
In one arrangement the material to be distributed is carried in a tank on the vehicle with a slot transversely of the vehicle through which the material can be discharged from the tank. The metering roller is then positioned in the slot for metering a curtain of the material which is dropped into a plurality of receptacles arranged along the length of the roller. The metered material from the receptacle is then transported pneumatically through tubes or ducts to spaced positions along the length of the booms extending on either side of the vehicle. The material is injected into the tube or duct from the receptacle using a venturi supplied with air from a fan on the vehicle. The tubes extend from the venturi and are confined to curve through the necessary changes of direction to the required position on the boom.
One problem which has caused considerable difficulty is that of supporting the booms on either side of the vehicle and for this purpose the booms are usually provided with one or more ground engaging wheel. This arrangement is unsatisfactory in that uneven ground can cause considerable deflection of the boom which not only strains the supporting structure but can also interfere with the even distribution of the fertilizer over the ground in view of the changing height of the boom from the ground.
A further problem which arises in arrangements of this type is that of maximizing the amount of material which can be carried or transported from the receptacles to the distribution points on the booms and at the same time minimizing the amount of air used to reduce the amount of power employed. It will be appreciated in this regard that if the amount of material transported in the airstream through tubes exceeds a predetermined maximum then the material can collect at various points in the tubes thus blocking off the system and halting proper distribution of the material.